Many conventional synthetic pathways exist for preparing amide compounds. For instance, the reaction of an amine and an ester in a solvent, a well-known basic organic reaction, can be used to form an amide. In particular, it is known that the formation of an amide linkage by the reaction of a primary amine with an ester in a solvent under heating is possible. Moreover, the formation of an amide by reacting a secondary amine and an ester, can require not only a solvent, but also a catalyst, such as Lewis acid, strong base, or enzyme.
From conventional methods, the syntheses of amides, such as N-substituted carbonyl alkylenediamines, have several common features outlined below.
(1) Typically, the starting material is the corresponding organic acid. The organic acid is activated to an acid chloride or acid anhydride of higher activity, which is then reacted with a diamine to form the desired N-substituted carbonyl alkylenediamine.
(2) Since acid chlorides or acid anhydrides are highly reactive, the diamine used, typically, is treated with hydrogen chloride, hydrogen bromide, acetic acid, or tert-butoxycarbonyl to protect one of the amine groups. This step helps to reduce the formation of undesired diamides. The desired N-substituted carbonyl alkylenediamine can be obtained by a de-protection step.
(3) The conventional synthesis, typically, requires at least four reaction steps to form the N-substituted carbonyl alkylenediamine product. Furthermore, the synthetic process does not have a desirably high yield of the N-substituted carbonyl alkylenediamine product (only about 40% to 70%), and chemical wastes are generated, thus causing environmental problems.